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      <title>滑动窗口的作用是什么？ - 交互式测验</title>
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          <div class="quiz-container">
            <div class="quiz-header">
              <h1>滑动窗口的作用是什么？ - 交互式测验</h1>
              <p>检验你对文档内容的理解程度</p>
            </div>
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      <script>
        const quizData = [
  {
    "question": "在TCP协议中，滑动窗口机制最主要的作用之一是什么？",
    "options": [
      "对传输的数据进行加密，以确保通信安全。",
      "实现流量控制，防止因发送速率过快导致接收端缓冲区溢出。",
      "在应用层将数据转换为统一的格式。",
      "为每个数据包选择最佳的网络路由路径。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "根据文档，滑动窗口的核心作用之一就是流量控制。它通过接收端反馈的窗口大小，来限制发送端可以发送的数据量，从而确保接收端有足够的时间和空间来处理收到的数据，避免了因处理不过来而导致的数据丢失（缓冲区溢出）。",
    "source": "文档中「1. 流量控制」部分",
    "hint": "思考一下，当接收方处理速度跟不上发送方时，会发生什么问题？滑动窗口是如何解决这个问题的？"
  },
  {
    "question": "在滑动窗口机制中，窗口的大小（Window Size）主要是由谁决定的，并通过什么方式告知发送方？",
    "options": [
      "由网络中的路由器根据拥塞情况决定，并通过ICMP报文通知。",
      "由发送端根据自身的发送能力决定，并在SYN报文中声明。",
      "由接收端的接收缓存容量决定，并通过ACK确认消息来通知。",
      "在TCP连接建立时由双方协商一个固定值，之后不再改变。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "文档中明确指出，窗口的大小由接收端的接收缓存容量决定。接收端在发送给发送端的ACK确认消息中，会包含其当前可用的窗口大小，发送端则根据这个值来调整自己的发送行为，以匹配接收端的处理能力。",
    "source": "文档中「1. 流量控制」部分的“窗口大小”",
    "hint": "“窗口大小：窗口的大小由接收端的接收缓存容量决定。接收端会在 ACK 消息中包含窗口大小信息...”"
  },
  {
    "question": "根据文档，滑动窗口机制是如何提高数据传输效率的？",
    "options": [
      "通过在传输前对数据进行高效压缩。",
      "允许发送端在未收到前一个数据包的确认（ACK）时，继续发送后续的多个数据包。",
      "通过减少TCP协议头部的字节数来降低网络开销。",
      "强制所有数据包都通过延迟最低的路径传输。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "滑动窗口机制提升效率的关键在于其“并行传输”的能力。它允许发送方一次性发送窗口大小内所有的数据包，而不需要每发送一个就停下来等待确认。这极大地减少了因等待ACK而造成的延迟，从而提高了网络带宽的利用率和整体传输速率。",
    "source": "文档中「3. 提高数据传输效率」部分",
    "hint": "如果每发送一个很小的数据包都要停下来等待对方的回复，效率会怎样？滑动窗口是如何改进这一点的？"
  },
  {
    "question": "关于滑动窗口的“动态调整”特性，以下哪项描述是正确的？",
    "options": [
      "窗口大小在TCP连接建立时设定，整个传输过程中保持不变。",
      "窗口大小会根据网络状况和接收端的处理能力自适应地进行调整。",
      "窗口大小仅由发送端根据网络延迟单方面调整。",
      "窗口大小的调整只在发生数据包丢失时才会触发。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "滑动窗口机制的核心优势之一就是其“自适应调整”能力。它不是一个静态的机制，而是会持续根据接收端在ACK中反馈的窗口大小以及网络拥塞情况（通过拥塞控制算法）来动态地放大或缩小，以适应不断变化的网络条件和接收端负载。",
    "source": "文档中「4. 动态调整」部分",
    "hint": "“滑动窗口机制是动态的，会根据网络的实际状况和接收端的处理能力调整窗口大小。”"
  },
  {
    "question": "滑动窗口在TCP的拥塞控制（Congestion Control）中扮演了什么角色？",
    "options": [
      "它完全取代了慢启动、拥塞避免等算法。",
      "它只负责流量控制，与网络拥塞没有任何关系。",
      "它通过与慢启动、拥塞避免等算法配合，共同调整发送窗口大小来管理网络资源。",
      "它通过提升数据包的优先级来避免被路由器丢弃。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "文档明确指出，滑动窗口在拥塞控制中也起着重要作用。它并非独立运作，而是与TCP的拥塞控制算法（如慢启动、拥塞避免）紧密配合。当算法检测到网络可能发生拥塞时，会通过调整（通常是减小）发送窗口的大小来限制数据发送速率，从而缓解网络压力。",
    "source": "文档中「5. 拥塞控制」部分",
    "hint": "思考一下流量控制（端到端）和拥塞控制（整个网络）的区别。滑动窗口是如何在这两者之间找到平衡的？"
  },
  {
    "question": "滑动窗口机制如何帮助实现TCP的“可靠数据传输”？",
    "options": [
      "通过对所有传输的数据进行端到端加密。",
      "通过数据确认（ACK）与超时重传机制的配合，确保数据包不丢失、不重复、按顺序到达。",
      "通过为每个数据包建立一条独立的备用连接。",
      "通过在数据发送前，先向接收端申请全部所需缓存空间。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "可靠性是TCP的核心特性。滑动窗口通过其内在的确认机制（ACK）来保证这一点。每个数据包都有序号，接收端按序确认。如果发送端在一定时间内没有收到某个数据包的ACK（超时），它就会启动重传机制。这种“确认+重传”的模式确保了数据的可靠交付。",
    "source": "文档中「6. 可靠数据传输」部分",
    "hint": "“滑动窗口的 ACK 机制确保了数据的可靠交付。......与超时重传机制配合使用，确保丢失的数据包能够重新发送和接收。”"
  }
];
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            const totalQuestions = quizData.length;
            const answeredCount = userAnswers.filter(a => a !== null).length;
            const wrongCount = answeredCount - correctCount;
            const skippedCount = totalQuestions - answeredCount;
            const accuracy = totalQuestions > 0 ? Math.round((correctCount / totalQuestions) * 100) : 0;
            const errorRate = totalQuestions > 0 ? Math.round((wrongCount / totalQuestions) * 100) : 0;

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                '<div class="score-card">' +
                '<h3>得分</h3>' +
                '<p>' + correctCount + ' / ' + totalQuestions + '</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>正确率</h3>' +
                '<p>' + accuracy + '%</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>错误率</h3>' +
                '<p>' + errorRate + '%</p>' +
                '</div>' +
                '<div class="score-card score-details">' +
                '<table>' +
                '<tr><td>正确</td><td>' + correctCount + '</td></tr>' +
                '<tr><td>错误</td><td>' + wrongCount + '</td></tr>' +
                '<tr><td>未答</td><td>' + skippedCount + '</td></tr>' +
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                '<div class="report-actions">' +
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        }

        function reviewQuiz() {
            const reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }

            document.querySelector('.quiz-body').style.display = 'block';
            document.getElementById('quiz-footer').style.display = 'flex';
            
            currentQuestionIndex = 0;
            loadQuestion();
            updateNavigationButtons(); // Ensure nav buttons are correctly displayed
        }

        // Event Delegation for options
        optionsListEl.addEventListener('click', (event) => {
            if (event.target && event.target.matches('li.option-item')) {
                // Check if the question has already been answered
                if (userAnswers[currentQuestionIndex] === null) {
                    const selectedIndex = parseInt(event.target.dataset.index, 10);
                    selectOption(selectedIndex);
                }
            }
        });

        prevBtn.addEventListener('click', goToPreviousQuestion);
        nextBtn.addEventListener('click', goToNextQuestion);
        hintBtn.addEventListener('click', showHint);
        
        // 初始加载
        loadQuestion();
      </script>
    </body>
    </html>
  